Typically, power plants include either a wet sump lubrication system or dry sump lubrication system.
In a wet sump lubrication system, oil is collected in an oil pan at the bottom of the crankcase after lubricating various engine components. The oil is then pumped directly from the oil pan to diverse locations requiring lubrication by means of an oil pump.
In a dry sump lubrication system, lubricant is removed or sucked from the crankcase before being recirculated to the power plant. Dry sump lubrication systems typically require less volumes of lubricant when compared to wet sump lubrication systems. In dry sump lubrication systems, blow-by gases may be used for conveying oil from the oil sump in the crankcase into an oil reservoir by way of an intake or riser line.
In dry sump lubrication systems, those skilled in the art recognize that it is desirable to maintain a negative pressure (or vacuum) within the crankcase. Other chambers connected to the crankcase, however, are not maintained under a negative pressure (or vacuum), because those skilled in the art do not perceive a benefit to such a construction.
German Patent No. DE 37 31 597 A1 describes one example of a dry sump lubrication system that relies on a controlled vacuum generator to ensure a vacuum in the crank chamber of an internal combustion engine. The controlled vacuum generator is assigned to a breather line emerging from the oil reservoir and opening into the intake pipe of the engine. The vacuum generator is connected by way of a signal line to a vacuum sensor in the crank chamber. The generator prevents leakage of gases and steam from the engine. The blow-by gases are forced from the combustion chamber of the engine into the crankcase during combustion. These blow-by gases must be dissipated or discharged to avoid a positive buildup of pressure within the engine.
European Patent No. EP 119135 A1 describes another example of a dry sump lubrication system. In this patent, a vacuum pump communicates with the crankcase. While the vacuum pump is in operation, blow-by gas in the crankcase is drained to the outside environment, whereby a negative pressure is created in the crankcase. The vacuum pump is provided to drain only the crankcase.
One drawback of the system described in this European patent lies in the fact that air may remain present in the crankcase during operation of the engine. During operation, the piston reciprocates within the cylinder, thereby performing the respective steps of intake, compression, combustion, and exhaust. When the engine is running, movement of the piston during intake (suction) and combustion (explosion) and the rotational motion of the connecting rod and the crankshaft are disturbed by the air in the crankcase, which reduces engine output. Furthermore, the air in the crankcase deteriorates the quality of the operation of the engine, because it may cause the lubricant to oxidize or deteriorate, which reduces the quality of the lubricant.
There have been numerous attempts to separate the crank chamber from other engine chambers, but none disclose maintaining two or more of these chambers under negative pressure. As indicated above, those skilled in the art do not recognize the benefit of such a construction.
For example, Japanese Patent Publication No. 61-182407 discloses the separation of a crank chamber and a transmission chamber. The chambers are connected via a reed valve. It is noted, however, that the transmission chamber is not held under negative pressure.
Similarly, Japanese Patent Publication No. 8-135419 discloses the separation of a crank chamber and the transmission chamber. The chambers are connected via an oil pump. As with the previous reference, the transmission chamber is not held under negative pressure.
Two other examples, U.S. Pat. Nos. 6,257,192 and 6,497,211, both disclose a crank chamber being separated from the transmission chamber. As with the Japanese examples, the transmission chamber is not held under negative pressure.
U.S. Pat. No. 6,497,211 discloses yet another arrangement. Here, a separate lubrication circuit is provided for each chamber. The different chambers are not held under negative pressure.
EP Patent Publication No. 1217182 discloses one further arrangement. Here, only the crank chamber held under negative pressure. The crankcase is separated from the transmission case. An oil pump drains oil from the crankcase and pumps the oil to the transmission case. From the transmission case, the oil flows into the lubrication tank, which is positioned below the transmission case. This arrangement is necessary because the transmission case cannot be positioned below the oil level in the lubrication tank. Otherwise, the oil would aggregate in the transmission case, which would be at the lowest position in the lubrication system.
One problem that is presented by the prior art lies in the fact that those skilled in the art have focused on separating the crankcase from the other chambers associated with the engine. As such, the prior art does not recognize the benefits of the present invention.